Migrant birds give spring an extra burst of color | SHARON SORENSON

In May, there's nothing prettier at the bird feeder than male goldfinches wearing brand-new bright gold suits, crisp black caps and newly painted yellow-orange bills. They feed next to male cardinals, which are attired in brilliantly royal crimson, seasonally bright to impress the girls.

Together, the two residents form a hurt-your-eyes, side-by-side gold-red that tops the gorgeous list. Nothing could be more striking.

Oops. Wrong. Add a male indigo bunting, decked out in intense blue, broadening the color spectrum. Mother Nature doesn't paint many creatures blue. When she does, it's an eyeful. So, with the indigo's arrival, there you have it — gold, red and blue, all vivid, all startlingly bright, all at the feeder.

The combination makes me catch my breath. I know absolutely nothing could be more stunning.

The migrant additions are all we need to prove that the color spectrum among springtime visitors brings the tropics to our doors.

And I've not yet mentioned Baltimore orioles, their fire-bright orange-and-black combo. Or scarlet tanagers, their startlingly black wings against all-over deep red. Or summer tanagers, their robes of orange-red. Or blue grosbeaks that wear their name.

But it's not a figure of speech to say these newly arrived rainbow birds bring us the tropics. They are, indeed, tropical birds. The bulk of their lives is spent in Central and South America. But come spring, they fly thousands of miles to come here to nest.

Why would they do that? Why not just stay in the tropics and save all the time and energy?

Most ornithologists agree that tropical birds come here to nest to reduce competition. Fewer birds live and nest here than in the tropics. So, here nest sites are more plentiful. But above all, food is more plentiful.

Certainly, the tropics boast lots of bugs, but lots of critters compete for them, especially during breeding season. Since almost all birds feed their babies bugs, the bug supply ranks critical for nestlings' health.

In addition, our summer days are longer than in the tropics. Longer daylight hours mean longer feeding times. More food means more babies. And more food makes babies grow faster.

By July or early August, it's all over for tropical parents. They leave, zip back to equatorial zones, leaving the kids to feast on more bugs, mature and gain strength.

Then, because they're born knowing where to go, how to get there and how to know when they've arrived, youngsters leave later, ultimately joining adults for a tropical winter.

In short, for tropical birds, migration is a cost-versus-benefits decision. As they evolved, migrants learned that nesting success offsets daunting migration risks.

So, tropical birds grace us with their colors, raising their babies on our bugs.

And every year their arrival reminds me that nothing can be prettier than a springtime feeder's rainbow, even beyond our beloved goldfinches and cardinals.

A lifelong area resident and backyard birder, Sharon Sorenson lives on a 3-acre certified backyard wildlife habitat and has more than 150 bird species on her yard list. Readers can contact her at forthebirdscolumn@yahoo.com.